An industrial shed kit is a pre-engineered steel package — portal frames, purlins and girts, cladding, fasteners and documentation — fabricated to a set of drawings and delivered for assembly on site. The two decisions that shape the whole build are clear span and wind region, because both are fixed at the design stage and neither can be changed afterwards.

What Actually Drives the Design of a Shed Kit

Australian shed kits look similar in a catalogue and behave very differently once the site is known. A shed in inland New South Wales and the same footprint on the north Queensland coast are not the same structure: the frames, the connections, the cladding fixings and the footings all change. Getting the specification right means starting from the site and the intended use rather than from a price per square metre.

Clear span sets the framing method. Clear span is the column-free width between portal frame legs, and it decides which framing approach is sensible. Cold-formed and RHS portal frames are commonly used for spans up to around 24 metres, with eave heights up to about 6 metres. Beyond roughly 24 metres a single RHS portal becomes less efficient, and universal beams or open-web trusses are usually specified instead, with universal beam portals remaining economical to around 40 metres. This is why 24 metres shows up repeatedly as a transition point in Australian shed design. For a farm shed storing headers and air seeders, or an industrial shed housing racking and a forklift aisle, the span you need is set by what has to move inside, not by what fits the budget.

Wind region is not a detail. AS/NZS 1170.2 divides Australia into wind regions, with Region A covering most inland, southern and central areas, Region B generally coastal, and Regions C and D covering the northern coastal areas exposed to cyclones. The 2021 revision refined this further, subdividing Region A and Region B and reassigning Tasmania. A shed rated for Region A and the same shed rated for Region C are different products in every meaningful sense — heavier frames, more connection capacity, different cladding fixing patterns and different tie-down requirements. Anyone quoting a single price for a shed without asking for the address has not yet engineered anything. Our wind and snow load design page explains how site wind inputs drive member sizing.

Terrain and topography sit on top of the region. The wind region is only the starting point. The standard then applies factors for terrain category — how built-up or open the surroundings are — and for topography, which is why a shed on an exposed ridge carries higher design pressures than an identical shed in a sheltered valley in the same region. Shielding from adjacent buildings can also be taken into account, but only where it genuinely exists and is likely to remain. This is the reason two neighbours in the same postcode can receive different engineering for the same shed, and it is a legitimate difference rather than a quoting inconsistency.

Hot-rolled and cold-formed are designed to different standards. AS 4100 is the Australian standard governing the design of structural steel members, and AS/NZS 4600 governs cold-formed steel structures, where thin sections behave differently because local buckling becomes a governing consideration well before the material yields. Most sheds combine both: a hot-rolled or fabricated portal frame carrying the building, with cold-formed purlins and girts spanning between frames and supporting the cladding. Knowing which standard applies to which member is what allows the documentation to be checked properly. Our steel building codes and standards page sets out how loading standards, material standards and the building code fit together.

What is in the kit and what stays local. A shed kit covers fabricated steelwork, secondary framing, cladding and flashings, fasteners and the drawing set. Footings, slab, site works, cranage and erection labour are local scope, quoted separately, and driven by ground conditions rather than by the kit. Certification is local scope as well. Under Queensland law, professional engineering services for a Queensland project must be carried out by a Registered Professional Engineer of Queensland, or under the direct supervision of one, and that requirement applies to work performed outside Queensland when it is intended for a Queensland project. GEMS 1749 supplies the kit and the supporting engineering documentation; the certification pathway and the RPEQ arrangement are settled project by project with the client and the local certifier.

Clear span

Typical framing approach

Common application

Up to 12 m

Cold-formed or RHS portal frame

Farm shed, workshop, small storage

15–18 m

RHS or light hot-rolled portal frame

Machinery shed, contractor workshop

Around 24 m

Upper range for single RHS portal efficiency

Larger machinery shed, storage with forklift access

30–40 m

Universal beam portal frame

Industrial shed, warehouse, processing

Spans above reflect general Australian practice for portal frame sheds. Actual member sizes depend on wind region, terrain, roof load and building geometry.

Machinery Sheds: Sizing Around the Equipment

A machinery shed is sized backwards from the largest machine that has to fit through the door and turn inside, then engineered for the wind at the site. Two sheds with identical footprints can carry very different frames once the site is applied, so the equipment list comes before the floor area.

Clear span before floor area. Clear span is the one decision that constrains everything downstream. Interior columns are cheaper to engineer, but they are obstacles you cannot move later, and in a machinery shed they stand exactly where a header, an air seeder or a boom sprayer needs to swing. Measure the widest implement in the position it will actually be stored, add working clearance on both sides, and treat that as the minimum span. Buying a narrower span to save money and then finding you cannot turn inside it is the most expensive mistake in this category, because a portal frame cannot be widened after fabrication.

Eave height and the door opening. Eave height is measured at the sidewall where the roof meets the wall, and it sets the practical limit on door height. Equipment does not care about eave height as such — it cares about the clear opening under the door header and the headroom needed to raise a tipper body, extend an auger or clear a chaser bin. Take the tallest machine in the position it will occupy inside the shed rather than its transport height, then add the clearance an operator needs to work around it. The door is an opening in a structural wall, and its framing has to be resolved before fabrication rather than cut in afterwards.

Bay spacing and shed length. Length is made up of bays — the distance between adjacent portal frames. Bay spacing is an engineering and economic decision rather than a free choice: wider bays mean fewer frames but heavier purlins and heavier frames, closer bays mean more frames but lighter secondary members. The optimum depends on the wind and roof loads at the site and on steel prices at the time of fabrication, which is why two suppliers can quote different bay spacings for the same shed and both be defensible. Length is cheap to add at the design stage and expensive to add later, so decide early whether you want room for a workshop bay, a parts store or machinery you have not bought yet.

Portal frame kit or pole shed. These are two different construction methods that often get discussed as the same product. A pole shed carries the roof on posts set into the ground, with the ground doing part of the structural work. A steel portal frame kit uses columns and rafters bolted together and held down to concrete footings, which resist the frame reactions including uplift. Pole construction is often cheaper for smaller rural sheds and tolerates simpler footings. Portal frames give longer clear spans, tighter tolerances and a straightforward path to compliance on larger buildings. Neither is universally better, and the honest comparison depends on span, use and what the local certifier expects to see.

The same logic outside Australia. Machinery sheds in the United States are sized the same way, with design loads taken from ASCE 7 and set by the exact site rather than by the state. Snow is mapped as a ground load and then adjusted for roof slope, exposure, thermal condition and drift, so a shed placed beside an existing taller barn can pick up a drift load that the same shed in open ground would never see. In both markets the kit is engineered to the address, and certification follows the rules of the place where the shed is built.

Frequently Asked Questions

What wind rating does my shed need?

That is set by your address, not chosen from a list. AS/NZS 1170.2 assigns a wind region, then terrain category and topography are applied to give site wind speeds. Regions C and D are cyclonic and require substantially more capacity throughout the structure. Supply the site address before comparing any two quotes, because ratings are not interchangeable.

Can an overseas supplier provide engineering for an Australian shed?

A supplier can fabricate to Australian standards and provide full documentation. Certification is a separate matter. In Queensland, professional engineering services for a Queensland project require a Registered Professional Engineer of Queensland, or direct supervision by one, including where the work is done overseas. Other states set their own arrangements, so check what applies to your site.

What is the difference between a farm shed and an industrial shed kit?

Mostly duty and specification rather than construction method. Both typically use portal frames. An industrial shed usually carries higher loads, larger openings, taller eaves and more services, and often faces stricter compliance expectations depending on occupancy. A farm shed with the same span may be lighter, but it is engineered to the same loading standard for its site.

What size machinery shed do I need for a header or a combine?

Measure your own machine rather than working from a published figure. Take the transport width with the header removed, add clearance to turn and to walk around it, and treat that as the minimum clear span. Header storage usually drives the length. Header widths and cab heights vary enough between makes and model years that a general number will mislead you.

Can I put up a machinery shed kit myself?

Bolted steel kits are designed to be assembled from the supplied erection drawings, and smaller sheds are sometimes owner-erected. Larger frames need lifting equipment, a trained crew and attention to the bracing sequence during erection, which is when the structure is at its most vulnerable. Most buyers use an experienced crew and treat erection as a separate line in the budget.

Related Guides

Wind and snow load design How site wind and snow inputs flow into frame, roof and connection sizing.

Codes and standards How loading standards, material standards and the building code fit together.

Foundation requirements Column reactions, anchor bolts, and the interface between the kit and local foundation design.

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